Add docs for extension config parameter for zend view renderer

[Xerkus]

Provide a narrative description of what you are trying to accomplish:

2.2.0 release of zendframework/zend-expressive-zendviewrenderer adds support for extension parameter for default suffix to be used by zend-view resolver, in line with other template renderers.

• [x] Is this related to documentation? Add documentation entry for extension config parameter.

[weierophinney]

This repository has been closed and moved to mezzio/mezzio; a new issue has been opened at https://github.com/mezzio/mezzio/issues/2.

[weierophinney]

This repository has been moved to mezzio/mezzio. If you feel that this patch is still relevant, please re-open against that repository, and reference this issue. To re-open, we suggest the following workflow:

• Squash all commits in your branch (git rebase -i origin/{branch})
• Make a note of all changed files (`git diff --name-only origin/{branch}...HEAD
• Run the laminas/laminas-migration tool on the code.
• Clone mezzio/mezzio to another directory.
• Copy the files from the second bullet point to the clone of mezzio/mezzio.
• In your clone of mezzio/mezzio, commit the files, push to your fork, and open the new PR. We will be providing tooling via laminas/laminas-migration soon to help automate the process.